YM, you have this thing about income not keeping up with debt, at the macro/Australia level. That seems to be the primary basis of your concern?
On what type of figures are you basing this - averages, across Australia? Given that you are into the technicals, have you looked at the distribution of both income & debt???? If both incomes and debt are both uniformly normally/gaussian distributed then yes you might be correct. I don't have the data, but I suspect (strongly) they aren't distributed in such a manner.
I suspect what you would find, if you were to really analyse the figures, is that in some locations/groups debt to income ratio is at quite an acceptable level, whilst in others, it is at horrendus levels. It might well be that it is the former, in the areas that they live, who are to a large extent driving prices there. In those areas there might not be no debt problems, and hence house price continue to rise. In other areas, there may be huge problems, and falls in house prices. After the debt problems in these problem areas blows up, then the Australia wide debt to income ratio (which you are so focused on) might fall.
Everybody has been telling you that it is the micro that matters. You've been dismissing it becasue of concern at the macro level, but surely this provides some sort technical/theoretical basis for dividing the macro into the various micro populations?